PURPOSE: To prevent polymerizable fluid from polymerizing in the pump, when it is transferred by using a slurry separation type caned motor pump and using the starting substance, the reaction solvent or the by-product on the production of the polymerizable liquid, as a back-flashing fluid.

CONSTITUTION: A slurry separation type caned motor pump using a back flushing fluid is employed for transferring a polymer, while non-polymerizable starting materials, the reaction solvent or the by-products in the polymerizable fluid is used as a back-flushing fluid to solve the problems on the transportation of the polymerizable fluid. The transportable polymerizable fluid is preferably acrylic acid, methacrylic acid or their esters. The back-flushing fluid is the starting material for production of the polymerizable fluid as well as the alcohol or a eutectic agent used in the production of the polymerizable fluid, water or high-boiling fraction formed as a by-product during the production. The starting substance and by-products are cooled to remove the heat generated inside the pump such as the motor or bearings effectively. This process causes no deterioration in quality and no pump seizing.